1. Technological Field
The subject of the invention is a novel process for depositing sensors, such as metals, biological molecules, on a porous support in a chosen pattern.
2. Description of the Related Art
The textile industry is seeking to develop what are called “smart” fabrics which make it possible, apart from the usual functions of textiles, to provide the fabric with additional functionalities. In certain projects deodorants or medicaments are incorporated into a fabric so as to diffuse over the course of time. In the clothing market, there are technical garments that include novel functionalities. For example, the company Mulliez has proposed garments for fixing odors, such as frying or perspiration odors. Other garments from the same company contain mosquito-repellant products intended in particular to prevent malaria. Other companies such as DIM or Triumph have proposed slimming or hydrating panty-hose based on capsules concealed between the fibers of the panty-hose.
Other developments relate to the implantation of electronic components in a garment, for example for cardiac monitoring. The practice of having the elderly remain in their own homes for as long as possible has inspired the development of sensors integrated into garments so as to monitor the physiological parameters of those persons to be monitored. Mention may also be made of an FM radio connected to the garment. Safety equipment or military suits are increasingly being equipped with sensors that measure the external environment (contamination, radioactivity) but also the physiological data of the person wearing the garment (heartbeat, temperature, stress, GPS positioning, etc.). Electrical or electrochemical sensors allow various physiological parameters to measured, such as for example the ionic conductivity of the patient's sweat, which may provide information about the latter's dehydration. Measurement of brain activity may be monitored by measuring the electrical activity of neurons (electroencephalogram). Temperature may be monitored by an electrical measurement, while pH may also be checked by electrochemical measurements. Monitoring of active medical treatments by reading biological responses via specific sensors may also be mentioned.
All these sensors require the use of metal electrodes for taking the measurement. The current approach consists in developing sensors and then attaching them to the garment by bonding, stitching or weaving. The sensors are therefore not integrated into the fabric, but attached thereto. The sensors are produced separately and then stitched or bonded to the garment and connected to the electronics integrated into the garment by electrical wires passed through the lining. This procedure represents an additional step in the production of the clothing article, and usually this step cannot be automated. It therefore represents an additional cost in the manufacture of the article. One way of improving this manufacturing process would consist in developing the sensor directly during manufacture of the fabric so as to push its integration to the maximum.
This requires precise definition of zones on a fabric for depositing thereon the materials or components intended to be integrated into the fabric. In particular, it is necessary beforehand to define not only the position of the sensor, but also its shape and size. If it is desired to be able to compare data delivered by various sensors, it is necessary to be able to determine the precise area of the sensor that will collect information. If it is desired to deliver a medicament, the area of exchange between the medicament-containing fabric and the skin must be able to be known precisely. The location of the components integrated into the garment and the area occupied by a sensor constitute elements of paramount importance in controlling the measurements made on a garment.
It is therefore necessary to be able to delimit zones in the fabric that will be dedicated to metallization or dedicated to the grafting, for example, of chemical or biological sensors.
Attempts have also been made to develop a process which overall simplifies garment manufacture in the case of garments that include electronic sensors, for example, by simultaneously creating the sensors and the contact mounting thereof. This avoids having to place connectors between the sensors and the electrical wires.
Hitherto, various methods have been employed for depositing metals on a porous material (fabric, paper, woven structure)—metal wires may be woven or stitched into the material during its manufacture. This technique is tricky as pure metals are generally ductile and brittle, and fabric manufacturing techniques are not always compatible for putting these metal wires in place. The cost of metal wires is high. The areas produced are generally of small size (less than 1 cm2).
Pure metals may be deposited in a sputterer or an evaporator through a mechanical mask. The fabric must then be able to be placed in a vacuum machine, and the cost of this operation is high. In addition, these physical deposition (evaporation, sputtering) techniques enable metal to be deposited only on the surface of the support. This is a major drawback during use of the support (for example washing or rubbing of the fabric). The material deposited risks being damaged and the resistivity of the sensor modified.
A third technique consists in using a printer, enabling a metallic ink to be deposited on the fabric at the chosen places. This technique allows pure metals to be deposited by chemical means, but requires the use of a printer. This technique can be envisioned if only a few patterns have to be manufactured, but as soon as it is desired to print several different patterns, this approach becomes time-consuming. In addition, the conductive ink spreads differently depending on the type of fabric in question. Since the hydrophilicity of the fabric depends on the woven fibers, the ink will wet the fabric to a greater or lesser extent, and the dimensions obtained will differ from one fabric to another.
To manufacture printed circuits, a support is coated with a copper layer on which a nickel or gold layer is deposited by a chemical or electrochemical process. In this case, the metal layer is deposited on the surface of the support and not in the thickness of the support. This technique is used for nonporous supports on which the copper tracks are obtained by chemical etching.
The manufacture of fabrics defining areas or volumes for metallization or for encapsulation of chemical or biological molecules may be carried out by the process of the invention, by means of a technique derived from screen printing.
Screen printing is a technique widely used in the manufacture of patterns on various supports (clothing, paper). This technique is used to print patterns on a fabric. A pattern is designed on a mesh. A color ink is deposited on the upper surface of the mesh and then scraped through the designed pattern so as to color the material positioned beneath the mesh. The deposited ink covers the surface of the fabric and is incorporated by capillary effect over a certain depth into the mesh cells of the fabric. Document WO 2006/011168 discloses a process for manufacturing silicone-based patterns on the upper part of a stocking so as to create a zone that enables the stocking to grip the legs without another fastening means. This process makes use of the screen printing technique.